The scene does not split for logic editing
When the cursor is in position to split the area, it should change to a cross.

If you have trouble dragging the corner, try  RMB on the edge of the editor and choosing split area.



To make clicking on the edge easier, you can change the line width to thick in the preferences.



Also of note is that in 2.80 the ability to split an area from the corners can be turned off.